Molecular Engineering of Azahomofullerene-based Electron Transporting Materials for Efficient and Stable Perovskite Solar Cells

Joanna Kruszyńska^a, Daniel Prochowicz^a

^aInstitute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland

Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV25)

Roma, Italy, 2025 May 12th - 14th

Organizers: Filippo De Angelis, Francesca Brunetti and Claudia Barolo

Poster, Joanna Kruszyńska, 045
Publication date: 17th February 2025

The rational molecular design of fullerene-based molecules with exceptional physical and electrical properties is in high demand to ensure efficient charge transport at the perovskite/electron transport layer interface.^[1] As a promising material, the fullerene derivative phenyl-C61-butyric acid methyl ester (PCBM) is commonly used as an interfacial carbon-based material to improve device performance and promote electron transfer.^[2-4] However, PCBM struggles to form uniform and dense films at the SnO₂/perovskite interface due to its high solubility in N,N-dimethylformamide (DMF) and weak interaction with SnO₂.^[5-7] Consequently, the nonuniform layer can enhance the recombination rate at the interface and serve as an ion migration channel, leading to device degradation.^[8] Additionally, PCBM films tend to aggregate under prolonged light or heat exposure, reducing the long-term stability of PSCs.^[9]

To address these issues, we designed, synthesized, and introduced a novel azahomofullerene (AHF) molecule as an interlayer for planar n–i–p PSCs. We demonstrated that the AHF molecule (denoted as AHF-4) exhibits stronger coordination with SnO₂ and better electronic coupling compared to PCBM, leading to improved perovskite film quality and reduced charge recombination in PSCs. As a result, our AHF-4-based device achieved a significantly higher efficiency (21.43%) with less hysteresis than the PCBM-based device (18.56%). Moreover, AHF-4-based devices demonstrated superior stability under continuous light exposure and elevated temperatures.^[1]

This work opens a new direction to the design of AHF derivatives with favorable physical and electrical properties as an interlayer material to improve both the performance and stability of PSCs.

References:

[1] Chavan R. D., Bończak B., Kruszyńska J., Mahapatra A., Ans M., Nawrocki J.,Nikiforow K., Yadav P., Paczesny J., Sadegh F.,Unal M., Akin S., Prochowicz D.; Molecular Engineering of Azahomofullerene-based Electron Transporting Materials for Efficient and Stable Perovskite Solar Cells. Chem. Mater. 2023, 35, 8309−8320

[2] Ke, W.; Zhao, D.; Xiao, C.; Wang, C.; Cimaroli, A. J.; Grice, C. R.; Yang, M.; Li, Z.; Jiang, C.-S.; Al-Jassim, M.; Zhu, K.; Kanatzidis, M. G.; Fang, G.; Yan, Y.; Cooperative Tin Oxide Fullerene Electron Selective Layers for High-Performance Planar Perovskite Solar Cells. J. Mater. Chem. A 2016, 4, 14276– 14283

[3] Fang, Y.; Bi, C.; Wang, D.; Huang, J.; The Functions of Fullerenes in Hybrid Perovskite Solar Cells. ACS Energy Lett. 2017, 2, 782– 794

[4] Liu, B.; Cui, R.; Huang, H.; Guo, X.; Dong, J.; Yao, H.; Li, Y.; Zhao, D.; Wang, J.; Zhang, J.; Chen, Y.; Sun, B.; Elucidating the Mechanisms Underlying PCBM Enhancement of CH3NH3PbI3 Perovskite Solar Cells Using GIXRD and XAFS. J. Mater. Chem. A 2020, 8, 3145– 3153

[5] Zhong, Y.; Hufnagel, M.; Thelakkat, M.; Li, C.; Huettner, S.; Role of PCBM in the Suppression of Hysteresis in Perovskite Solar Cells. Adv. Funct. Mater. 2020, 30, 1908920

[6] Huang, S.-K.; Wang, Y.-C.; Ke, W.-C.; Kao, Y.-T.; She, N.-Z.; Li, J.-X.; Luo, C.-W.; Yabushita, A.; Wang, D.-Y.; Chang, Y. J.; Tsukagoshi, K.; Chen, C.-W.; Unravelling the Origin of the Photocarrier Dynamics of Fullerene-Derivative Passivation of SnO2 Electron Transporters in Perovskite Solar Cells. J. Mater. Chem. A 2020, 8, 23607– 23616

[7] Wang, J.; Datta, K.; Weijtens, C. H. L.; Wienk, M. M.; Janssen, R. A. J.; Insights into Fullerene Passivation of SnO2 Electron Transport Layers in Perovskite Solar Cells. Adv. Funct. Mater. 2019, 29, 1905883

[8] You, S.; Zeng, H.; Liu, Y.; Han, B.; Li, M.; Li, L.; Zheng, X.; Guo, R.; Luo, L.; Li, Z.; Zhang, C.; Liu, R.; Zhao, Y.; Zhang, S.; Peng, Q.; Wang, T.; Chen, Q.; Eickemeyer, F. T.; Carlsen, B.; Zakeeruddin, S. M.; Mai, L.; Rong, Y.; Grätzel, M.; Li, X.; Radical Polymeric P-Doping and Grain Modulation for Stable, Efficient Perovskite Solar Modules. Science 2023, 379, 288– 294

[9] Li, S.-H.; Xing, Z.; Wu, B.-S.; Chen, Z.-C.; Yao, Y.-R.; Tian, H.-R.; Li, M.-F.; Yun, D.-Q.; Deng, L.-L.; Xie, S.-Y.; Huang, R.-B.; Zheng, L.-S.; Hybrid Fullerene-Based Electron Transport Layers Improving the Thermal Stability of Perovskite Solar Cells. ACS Appl. Mater. Interfaces 2020, 12, 20733– 20740

Acknowledgements:

J. K. and D.P. acknowledge the National Science Centre (grant SONATA BIS 10, no. 2020/38/E/ST5/00267) for financial support.

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